US8513171B2 - Lubricant composition, speed reduction gear, and electric power steering apparatus - Google Patents

Lubricant composition, speed reduction gear, and electric power steering apparatus Download PDF

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US8513171B2
US8513171B2 US13/119,029 US200913119029A US8513171B2 US 8513171 B2 US8513171 B2 US 8513171B2 US 200913119029 A US200913119029 A US 200913119029A US 8513171 B2 US8513171 B2 US 8513171B2
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lubricant composition
speed reduction
reduction gear
gear
zinc stearate
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US20110168479A1 (en
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Ryuji Nakata
Miwa Hokii
Mitsuhiro Kakizaki
Daisuke Tsutsui
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Kyodo Yushi Co Ltd
JTEKT Corp
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Kyodo Yushi Co Ltd
JTEKT Corp
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Assigned to JTEKT CORPORATION, KYODO YUSHI CO., LTD. reassignment JTEKT CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KAKIZAKI, MITSUHIRO, TSUTSUI, DAISUKE, HOKII, MIWA, NAKATA, RYUJI
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M161/00—Lubricating compositions characterised by the additive being a mixture of a macromolecular compound and a non-macromolecular compound, each of these compounds being essential
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2205/00—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions
    • C10M2205/02—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers
    • C10M2205/028—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers containing aliphatic monomers having more than four carbon atoms
    • C10M2205/0285—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers containing aliphatic monomers having more than four carbon atoms used as base material
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
    • C10M2207/08—Aldehydes; Ketones
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
    • C10M2207/10—Carboxylix acids; Neutral salts thereof
    • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
    • C10M2207/125—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids
    • C10M2207/126—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids monocarboxylic
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
    • C10M2215/02—Amines, e.g. polyalkylene polyamines; Quaternary amines
    • C10M2215/06—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to carbon atoms of six-membered aromatic rings
    • C10M2215/064—Di- and triaryl amines
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
    • C10M2215/02—Amines, e.g. polyalkylene polyamines; Quaternary amines
    • C10M2215/06—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to carbon atoms of six-membered aromatic rings
    • C10M2215/064—Di- and triaryl amines
    • C10M2215/065—Phenyl-Naphthyl amines
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
    • C10M2215/22—Heterocyclic nitrogen compounds
    • C10M2215/223—Five-membered rings containing nitrogen and carbon only
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
    • C10M2215/22—Heterocyclic nitrogen compounds
    • C10M2215/223—Five-membered rings containing nitrogen and carbon only
    • C10M2215/224—Imidazoles
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2217/00—Organic macromolecular compounds containing nitrogen as ingredients in lubricant compositions
    • C10M2217/04—Macromolecular compounds from nitrogen-containing monomers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • C10M2217/045—Polyureas; Polyurethanes
    • C10M2217/0456—Polyureas; Polyurethanes used as thickening agents
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
    • C10M2219/04—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions containing sulfur-to-oxygen bonds, i.e. sulfones, sulfoxides
    • C10M2219/046—Overbasedsulfonic acid salts
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
    • C10M2219/06—Thio-acids; Thiocyanates; Derivatives thereof
    • C10M2219/062—Thio-acids; Thiocyanates; Derivatives thereof having carbon-to-sulfur double bonds
    • C10M2219/066—Thiocarbamic type compounds
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
    • C10M2219/10—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring
    • C10M2219/104—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring containing sulfur and carbon with nitrogen or oxygen in the ring
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
    • C10M2219/10—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring
    • C10M2219/104—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring containing sulfur and carbon with nitrogen or oxygen in the ring
    • C10M2219/106—Thiadiazoles
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
    • C10M2219/10—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring
    • C10M2219/104—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring containing sulfur and carbon with nitrogen or oxygen in the ring
    • C10M2219/108—Phenothiazine
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2223/00—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions
    • C10M2223/02—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions having no phosphorus-to-carbon bonds
    • C10M2223/049—Phosphite
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
    • C10N2030/08—Resistance to extreme temperature
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
    • C10N2030/36—Seal compatibility, e.g. with rubber
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
    • C10N2030/74—Noack Volatility
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2040/00—Specified use or application for which the lubricating composition is intended
    • C10N2040/04—Oil-bath; Gear-boxes; Automatic transmissions; Traction drives
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2050/00—Form in which the lubricant is applied to the material being lubricated
    • C10N2050/10—Semi-solids; greasy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H57/00—General details of gearing
    • F16H57/04—Features relating to lubrication or cooling or heating
    • F16H57/048—Type of gearings to be lubricated, cooled or heated
    • F16H57/0498—Worm gearings
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/19—Gearing
    • Y10T74/19642—Directly cooperating gears

Definitions

  • the present invention relates to a lubricant composition that can be used favorably, for example, in a speed reduction gear, which includes a small gear and a large gear, or in a rolling bearing, ball screw, etc., and also relates to a speed reduction gear filled with the lubricant composition and an electric power steering apparatus incorporating the speed reduction gear.
  • a speed reduction gear is used in an electric power steering apparatus of an automobile.
  • a rotation of an electric motor is reduced in speed and amplified in output by being transmitted from a small gear, such as a worm gear, to a large gear, such as a worm wheel, in the speed reduction gear and is thereafter imparted to a steering shaft to perform torque assist of a steering operation.
  • a region of the speed reduction gear that includes at least a portion of engagement of the small gear and the large gear is filled with grease or other lubricant composition for lubrication.
  • a thickener such as a urea thickener
  • an additive such as a low friction additive
  • a base oil such as a synthetic hydrocarbon oil
  • a metal soap such as lithium stearate and calcium stearate
  • lithium stearate is especially excellent in function as a low friction additive, that is, in the function of lowering a friction coefficient of the lubricant composition and is thus used widely (see, for example, Patent Documents 1 and 2).
  • a lubricant composition that contains lithium stearate By using a lubricant composition that contains lithium stearate, an efficiency of speed reduction in a speed reduction gear can be improved and a torque of an electric power steering apparatus incorporating the speed reduction gear can be reduced to improve a steering sensation of an automobile incorporating the electric power steering apparatus.
  • a conventional lubricant composition that contains lithium stearate expresses an attacking property against polyamide resin, etc., that is popularly used as a component material of mechanical parts in mechanical fields and may cause a problem of shortening a durability life of a mechanical part (for example, a gear) made of the polyamide resin, etc.
  • Zinc stearate is known as a metal soap, which, when contained in a lubricant composition, can function as a satisfactory low friction additive substantially equivalent to lithium stearate (see, for example, Patent Documents 3 to 5). Also, according to examination by the inventors, zinc stearate provides an action of alleviating the attacking property against polyamide resin, etc. Use of a lubricant composition containing zinc stearate in place of lithium stearate in combination with a gear, etc., made of polyamide resin, etc., can thus be considered.
  • Patent Document 1 Japanese Published Unexamined Patent Application No. 2004-83797
  • Patent Document 2 Japanese Published Unexamined Patent Application No. 2004-314916
  • Patent Document 3 Japanese Published Unexamined Patent Application No. 9-104889
  • Patent Document 4 Japanese Published Unexamined Patent Application No. 10-88167
  • Patent Document 5 Japanese Published Unexamined Patent Application No. 2007-100107
  • zinc stearate in itself is not adequately heat resistant in comparison to other metal soaps, such as lithium stearate, and readily undergoes oxidative deterioration when contained in a lubricant composition and used under a high temperature environment, such as in a periphery of an engine of an automobile.
  • zinc stearate undergoes oxidative deterioration its function particularly as a low friction additive degrades or is lost readily in a short term.
  • a lubricant composition that is low in friction and can maintain satisfactory lubrication while suppressing deterioration of polyamide resin, etc., and is yet excellent in heat resistance is demanded.
  • This demand is not restricted to the speed reduction gear but applies likewise to a rolling bearing, ball screw, etc., having, for example, a retainer formed of polyamide resin, etc.
  • An object of the present invention is to provide a lubricant composition, which is low in friction, does not have an attacking property against polyamide resin, etc., is excellent in heat resistance, and especially does not undergo deterioration or loss of the respective characteristics in a short term when used under a high temperature environment, and to provide a speed reduction gear and an electric power steering apparatus that use the lubricant composition.
  • a sulfur-based antioxidant as an antioxidant along with using a synthetic hydrocarbon oil as the base oil. That is, a sulfur-based antioxidant not only has a function of decomposing peroxides to prevent oxidation and thereby provide an action of suppressing the oxidative deterioration of zinc stearate in the lubricant composition but also suppresses deterioration of polyamide resin, etc., by this function and furthermore functions as an anti-wear agent.
  • a sulfur-based antioxidant be contained as an antioxidant along with zinc stearate in a synthetic hydrocarbon oil, which does not readily degrade a polyamide resin due to not having a polar group in the molecule
  • a lubricant composition which is low in friction, does not have an attacking property against polyamide resin, etc., and is excellent in heat resistance, can be provided beyond the effect of having simply selected the antioxidant.
  • the present invention thus provides a lubricant composition that includes at least a synthetic hydrocarbon oil, a urea thickener, zinc stearate, and a sulfur-based antioxidant.
  • zinc stearate is made to function as a thickener as well.
  • the lubricant composition can thereby be made even lower in friction, not to have an attacking property against polyamide resin, etc., and yet excellent in heat resistance.
  • zinc stearate is not added afterwards to the lubricant composition in a form of a powder but zinc stearate is completely dissolved in the synthetic hydrocarbon oil that is the base of the lubricant composition to form a grease.
  • the sulfur-based antioxidant at least one type of compound selected from the group consisting of benzothiazole compounds, dithiocarbamate compounds, and benzimidazole compounds is preferable. All of these compounds prevent oxidative deterioration of zinc stearate, are excellent in the above-described function of suppressing the deterioration of polyamide resin, etc., and also function satisfactorily as anti-wear agents.
  • the lubricant composition can thus be made even lower in friction, not to have an attacking property against polyamide resin, etc., and yet excellent in heat resistance.
  • the lubricant composition according to the present invention includes a rust inhibitor and the rust inhibitor is a benzotriazole compound.
  • a benzotriazole compound does not have a function of promoting oxidative deterioration of zinc stearate and the heat resistance of the lubricant composition can thus be improved further while satisfactorily rustproofing a metal portion of the speed reduction gear, etc.
  • a speed reduction gear according to the present invention includes a small gear and a large gear that are mutually engaged and, due to a region including at least a portion of engagement of the small gear and the large gear being filled with the lubricant composition of the present invention, is excellent in speed reduction efficiency and, especially in a case where gears made of polyamide resin, etc., are used to achieve light weight, is capable of maintaining the speed reduction efficiency in a satisfactory range over a long term while preventing deterioration of the gears.
  • an electric power steering apparatus includes an electric motor, which assists steering of a steering mechanism of an automobile, and the speed reduction gear, and because an output of the electric motor is transmitted to the steering mechanism via the speed reduction gear, a torque of the electric power steering apparatus can be reduced while suppressing deterioration of the gears made of polyamide resin, etc., to thereby enable an effect of improving a steering sensation of the automobile incorporating the electric power steering apparatus to be maintained satisfactorily over a long term.
  • a lubricant composition which is low in friction, does not have an attacking property against polyamide resin, etc., is excellent in heat resistance, and especially does not undergo deterioration or loss of the respective characteristics in a short term when used under a high temperature environment, can be provided along with a speed reduction gear and an electric power steering apparatus that use the lubricant composition.
  • FIG. 1 is a schematic view of an electric power steering apparatus according to an embodiment of the present invention.
  • a lubricant composition according to the present invention includes at least a synthetic hydrocarbon oil, a urea thickener, zinc stearate, and a sulfur-based antioxidant.
  • poly- ⁇ -olefin obtained by restrictingly polymerization just a few molecules of a straight-chain ⁇ -olefin having 6 to 18 carbons and then hydrogenating residual unsaturated double bonds, etc., can be cited.
  • the poly- ⁇ -olefin or other synthetic hydrocarbon oil preferably has kinematic viscosity of no less than 18 mm 2 /s and no more than 64 mm 2 /s and especially preferably no less than 30 mm 2 /s and no more than 48 mm 2 /s.
  • a lubricant composition capable of suppressing increase in rotational torque with minimal friction over a wide temperature range and is excellent in lubricity due to having an adequate oil film thickness can thereby be formed.
  • a content proportion of the synthetic hydrocarbon oil in a total amount of the lubricant composition is a remainder of subtraction of the other components forming the lubricant composition. That is, the content proportion of the synthetic hydrocarbon oil is set so that the total amount resulting from adding the synthetic hydrocarbon to predetermined amounts of the other components is 100% by mass.
  • urea thickener any of various urea thickeners, such as diurea, triurea, and tetraurea thickeners, maybe used and a diurea thickener is especially preferable.
  • a diurea thickener has a structure expressed by Formula (1):
  • R 1 indicates a diisocyanate residue and R 2 and R 3 indicate amine residues that may be the same or different]
  • R 1 indicates a diisocyanate residue and R 2 and R 3 indicate amine residues that may be the same or different]
  • R 1 , R 2 , and R 3 are as described above.
  • the reaction is preferably carried out in the synthetic hydrocarbon oil that is the base of the lubricant composition, and a lubricant composition of higher uniformity is thereby obtained.
  • the diisocyanate compound (2) and the amine compounds (3) and (4) are dissolved separately in the synthetic hydrocarbon oil to prepare a diisocyanate solution and an amine solution.
  • the diurea thickener expressed by Formula (1) is then synthesized by gradually adding one of the solutions to the other solution while stirring to make the diisocyanate compound (2) and the amine compounds (3) and (4) react.
  • the synthetic hydrocarbon oil is made into a grease by the synthesized diurea thickener.
  • the diurea thickener As favorable examples of the diurea thickener, one type or two or more types of reaction product among a reaction product of 4,4′-diphenylmethane diisocyanate, an alkyl phenyl amine in which the number of carbons of the alkyl portion is 8 to 18 (p-dodecylamine, etc.), and cyclohexylamine, a reaction product of the 4,4′-diphenylmethane diisocyanate, stearylamine (octadecylamine), and oleylamine, and a reaction product of the 4,4′-diphenylmethane diisocyanate, stearylamine, and octylamine can be cited.
  • a content proportion of the urea thickener may be changed as suited according to usage conditions, etc., of the lubricant composition, and for example in a case of use for lubrication of a speed reduction gear to be used upon incorporation in an electric power steering apparatus, the content proportion is preferably no less than 7% by mass and no more than 10% by mass and especially preferably no less than 8% by mass and no more than 9% by mass of the total amount of the lubricant composition.
  • so-called oil separation with which the synthetic hydrocarbon oil separates from the grease, may occur readily, and when the above range is exceeded, the torque of the electric power steering apparatus may increase.
  • Zinc stearate is added in a powder state to the lubricant composition and made to function as a low friction additive, etc., or preferably made to function as a thickener in addition to being made to function as the low friction additive, etc., and in the latter case, zinc stearate is completely dissolved in the synthetic hydrocarbon oil that is the base of lubricant composition to form a grease as described above.
  • a predetermined amount of zinc stearate is blended into the synthetic hydrocarbon oil and after heating while stirring to completely dissolve the zinc stearate, the mixture is cooled to room temperature while continuing to stir to thereby prepare a grease containing the zinc stearate as the thickener (may hereinafter be referred to in brief as “zinc stearate grease”).
  • the zinc stearate grease and a grease containing the diurea thickener synthesized, for example, by the above reaction are then blended at predetermined proportions, stirred, and kneaded using a homogenizer, a three-roll mill, etc., to obtain the lubricant composition containing both the urea thickener and zinc stearate as the thickener.
  • sulfur-based antioxidant and other additives are preferably added after preparation of the diurea grease and the zinc stearate grease or after mixing both greases, a component that does not inhibit the synthesis reaction of the diurea thickener, the forming of the grease by zinc stearate, etc., may be blended in the synthetic hydrocarbon oil in advance.
  • a content proportion of zinc stearate may be changed as suited according to the usage conditions, etc., of the lubricant composition.
  • the content proportion is preferably no less than 3% by mass and no more than 10% by mass and especially preferably no less than 5% by mass and no more than 8% by mass of the total amount of the lubricant composition.
  • any of various compounds having a function of decomposing peroxides by the sulfur contained in the molecule and thereby preventing oxidative deterioration of zinc stearate and suppressing deterioration of polyamide resin, etc., may be used.
  • a benzothiazole compound a dithiocarbamine compound, and a benzimidazole compound can be cited.
  • the benzothiazole compound which has a benzothiazole expressed by Formula (5) as a basic skeleton functions as antioxidant.
  • the dithiocarbamine compound which has a dithiocarbamic acid residue expressed by Formula (6) as a basic skeleton functions as antioxidant.
  • the benzimidazole compound which has a benzimidazole expressed by Formula (7) as a basic skeleton functions as antioxidant.
  • One type of the above compounds may be used solitarily or two or more types may be used in combination.
  • benzothiazole compound one type or two or more types of compound among 2-mercaptobenzothiazole or a zinc salt thereof, dibenzothiazyl disulfide, etc., can be cited, and 2-mercaptobenzothiazole is especially preferable.
  • a content proportion of 2-mercaptobenzothiazole is preferably no less than 0.25% by mass and no more than 2% by mass and especially preferably no less than 0.5% by mass and no more than 2% by mass of the total amount of the lubricant composition.
  • a content proportion of dibenzothiazyl disulfide is preferably no less than 1% by mass and no more than 4% by mass and especially preferably no less than 2% by mass and no more than 4% by mass of the total amount of the lubricant composition.
  • a function of the benzothiazole compound of preventing the oxidative deterioration of zinc stearate and suppressing the deterioration of polyamide resin, etc., a function as an anti-wear agent, etc. maybe inadequate.
  • a friction coefficient of the lubricant composition may be large and the torque of the electric power steering apparatus, etc., may increase.
  • dithiocarbamine compound one type or two or more types of compound among dibutyldithiocarbamate, methylene-bis-dibutyldithiocarbamate, etc., can be cited.
  • a content proportion of the dithiocarbamine compound is preferably no less than 0.5% by mass and no more than 3% by mass and especially preferably no less than 1% by mass and no more than 3% by mass of the total amount of the lubricant composition.
  • the function of the dithiocarbamine compound of preventing the oxidative deterioration of zinc stearate and suppressing the deterioration of polyamide resin, etc., function as an anti-wear agent, etc. maybe inadequate.
  • the friction coefficient of the lubricant composition may be large and the torque of the electric power steering apparatus, etc., may increase.
  • benzimidazole compound one type or two or more types of compound among 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, 4-mercaptomethylbenzimidazole, 5-mercaptomethylbenzimidazole, and zinc salts of these, etc., can be cited.
  • a content proportion of the benzimidazole compound is preferably no less than 0.5% by mass and no more than 3% by mass and especially preferably no less than 1% by mass and no more than 3% by mass of the total amount of the lubricant composition.
  • the function of the benzimidazole compound of preventing the oxidative deterioration of zinc stearate and suppressing the deterioration of polyimide resin, etc., a function as an anti-wear agent, etc. may be inadequate.
  • the friction coefficient of the lubricant composition may be large and the torque of the electric power steering apparatus, etc., may increase.
  • a favorable range of the total content proportion of the compounds is determined in consideration of the preferable ranges for the respective compounds.
  • the lubricant composition according to the present invention may contain other additives besides the above.
  • a rust inhibitor a metal deactivator, a viscosity index improver, an oiliness agent, etc.
  • a rust inhibitor one type or two or more types of rust inhibitors among benzotriazole compounds, calcium sulfonate-based rust inhibitors, etc., can be cited, and a benzotriazole compound is especially preferable.
  • the benzotriazole compound does not have the function of promoting oxidative deterioration of zinc stearate and can thus further improve the heat resistance of the lubricant composition while satisfactorily rustproofing a metal portion of a speed reduction gear, etc.
  • benzotriazole compounds one type or two or more types of compound among benzotriazole, which is expressed by Formula (8), 1-[N,N-bis(2-ethylhexyl)aminomethyl]-9-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-5-benzotriazole, etc., can be cited.
  • a content proportion of the benzotriazole compound is preferably no less than 0.01% by mass and no more than 0.5% by mass and especially preferably no less than 0.05% by mass and no more than 0.1% by mass of the total amount of the lubricant composition.
  • the content proportion is less than the above range, the function of the benzotriazole compound as a rust inhibitor may not be obtained adequately, and in the case where the above range is exceeded, a friction coefficient of the lubricant composition may be large.
  • a consistency of the lubricant composition may be set in a suitable range in accordance with usage.
  • the consistency at a measurement temperature of 40° C. is preferably No. 2 to No. 1 as expressed as an NLGI (National Lubricating Grease Institute) number.
  • a lubricant composition that is harder than the above range may increase the torque of the electric power steering apparatus, etc., and a lubricant composition that is softer than the above range may cause leakage from the electric power steering apparatus, etc., or cause oil separation.
  • FIG. 1 is a schematic view showing the configuration of an embodiment of an electric steering apparatus according to the present invention.
  • the electric steering apparatus 1 has a steering shaft 3 connected to a steering member 2 , such as a steering wheel, an intermediate shaft 5 connected to the steering shaft 3 through a universal joint 4 , a pinion shaft 7 connected to the intermediate shaft 5 through a universal joint 6 , and a rack bar 8 having rack teeth 8 a meshed with pinion teeth 7 a provided of the pinion shaft 7 and extending along the right and left of an automobile.
  • the pinion shaft 7 and the rack bar 8 constitute a rack-and-pinion mechanism serving as a steering mechanism 9 .
  • the rack bar 8 is supported so as to be linearly movable right and left through a plurality of bearings (not shown) within a rack housing 10 fixed to an automobile body. Both ends of the rack bar 8 are projected toward both the sides of the rack housing 10 , and a tie rod 11 is coupled to each of the projected ends. Each of the tie rods 11 is connected to a corresponding steerable wheel 12 through a corresponding knuckle arm (not shown).
  • the steering member 2 is operated to rotate the steering shaft 3 , the rotation is converted into the linear motion of the rack bar 8 along the right and left of the automobile by the pinion teeth 7 a and the rack teeth 8 a to turn the steerable wheel 12 .
  • the steering shaft 3 is divided into an input shaft 3 a communicating with the steering member 2 and an output shaft 3 b communicating with the pinion shaft 7 . Both the shafts 3 a and 3 b are connected to each other so as to be relatively rotatable on the same axis through a torsion bar 13 .
  • the torsion bar 13 is provided with a torque sensor 14 for detecting a steering torque from a displacement amount of relative rotation between both the shafts 3 a and 3 b . The results of the detection of the torque by the torque sensor 14 are given to an ECU (Electric Control Unit) 15 .
  • ECU Electronic Control Unit
  • the ECU 15 controls the driving of an electric motor 17 for steering assist through a driving circuit 16 on the basis of the results such as the detection of the torque and the detection of automobile speed given from an automobile speed sensor (not shown), for example.
  • the output rotation of the electric motor 17 is reduced through a speed reduction gear 18 , is transmitted to the pinion shaft 7 , and is converted into the linear motion of the rack bar 8 to assist steering.
  • the speed reduction gear 18 comprises a small gear 19 serving as an input shaft whose rotation is driven by the electric motor 17 , and a large gear 20 meshed with the small gear 19 and connected to the output shaft 3 b in the steering shaft 3 so as to be integrally rotatable.
  • a meshing portion of the small gear 19 and the large gear 20 is filled with the lubricant composition according to the present invention.
  • the lubricant composition according to the present invention does not have attacking property against polyamide resin, etc., especially under a high temperature environment, such as in a periphery of an engine of an automobile, as described previously. Therefore, when at least one of the small gear 19 and the large gear 20 of the speed reduction gear 18 , especially the teeth portion of the large gear 20 is formed by the polyamide resin, etc., the lubricant composition does not have a possibility of reducing durability life of the teeth portion. Since the lubricant composition is low in friction, an efficiency of speed reduction in the speed reduction gear 18 can be improved and a torque of the electric power steering apparatus 1 incorporating the speed reduction gear 18 can be reduced to improve a steering sensation of an automobile incorporating the electric power steering apparatus 1 . Moreover, since the lubricant composition is excellent in heat resistance, and does not undergo deterioration or loss of the respective characteristics in a short term when used under a high temperature environment.
  • Polyamide resin (Nylon 6, Nylon 46, Nylon66, etc.) is mentioned as resin which is effective combining the lubricant composition according to the present invention. Moreover, polyacetal resin (POM), acrylonitrile-butadiene-styrene copolymer (ABS), polycarbonate resin, etc. are also mentioned as the above-mentioned resin.
  • POM polyacetal resin
  • ABS acrylonitrile-butadiene-styrene copolymer
  • ABS polycarbonate resin
  • the present invention is not limited to the above-mentioned embodiment.
  • the speed reduction gear the speed reduction gear containing warm and warm wheel explained previously is mentioned.
  • the speed reduction gear containing other gear train such as helical gears and spur gears, are also mentioned.
  • the lubricant composition according to the present invention can be used as lubricant of other drive transfer mechanisms in which it has gear train containing two or more gears which mesh mutually, other than the speed reduction gear. Moreover, the lubricant composition can be used also as lubricant of rolling bearing or ball screw, as explained previously.
  • the speed reduction gear according to the present invention can be used as a speed reduction gear of devices other than the electric power steering apparatus. Furthermore, various change can be given within the limits of the matter described by the claim of this invention.
  • PAO-8 having a kinematic viscosity at 40° C. of 48 mm 2 /s and a kinematic viscosity at 100° C. of 7.9 mm 2 /s.
  • a diurea grease prepared according to “Preparation of diurea grease” below was used.
  • Diphenylmethane-4,4-diisocyanate was blended into the poly- ⁇ -olefin and heated to 70 to 80° C. while stirring. Meanwhile, octylamine and stearylamine were blended into the poly- ⁇ -olefin and heated to 70 to 80° C. while stirring. The latter mixture was then added to the former mixture while maintaining the temperature and then first reacted for 30 minutes at 100 to 110° C. while continuing to stir, then raised in temperature to 160 to 170° C., and thereafter allowed to cool to prepare the diurea grease.
  • a blend ratio of diphenylmethane-4,4-diisocyanate, octylamine, and stearylamine was 1:1:1 as a molar ratio.
  • a mass ratio of the diurea thickener and the poly- ⁇ -olefin in the diurea grease prepared was: diurea thickener: poly- ⁇ -olefin-15:85.
  • a zinc stearate grease prepared according to “Preparation of zinc stearate grease” below was used.
  • Hindered amine-based antioxidant Alkyldiphenylamine-based compound (reaction product of diphenylamine and 2,4,4-trimethylpentene)
  • Hindered amine-based antioxidant Phenyl- ⁇ -naphthylamine (N-phenyl-1,1,3,3-tetramethylbutyl naphthalene-amine)
  • Phosphorus-based antioxidant Tridecyl phosphite
  • Test pieces type IA defined in Japanese Industrial Standards JIS K7162: 1994 (IS0527-2:1993) “Plastics—Determination of tensile propertie—Part 2: Test conditions for moulding and extrusion plastic” were prepared by injection molding nylon-66.
  • ⁇ B0 is the tensile failure strain of a test piece that is not dipped in a lubricant composition
  • the extension retention was no less than 25%. Does not have attacking property.
  • the extension retention was less than 25%. Has attacking property.
  • SPCC-SD normal steel plates
  • the evaporation amount was less than 12.2%. Small evaporation amount.
  • the evaporation amount was no less than 12.2%. Large evaporation amount.
  • the evaporation amount was low and the change of tint was small. Satisfactory heat resistance.
  • the heat resistance is satisfactory.
  • the evaporation amount was low and the change of tint was medium or large, or the evaporation amount was high and the change of tint was small. Normal level heat resistance.
  • the evaporation amount was high and the change of tint was large. Poor heat resistance.
  • a lubricant composition was produced in the same manner as in Comparative Example 1 and evaluated as described above for the attacking property and the heat resistance.
  • lubricant compositions were produced in the same manner as in Examples 1 to 3 and 5 and then evaluated for the attacking property and the heat resistance. The results are shown in Table 2.
  • Example 11 Besides setting the amount of the benzothiazole compound (S1) as the antioxidant to 0.25 g (Example 11), 1 g (Example 12), and 2 g (Example 13), lubricant compositions were produced in the same manner as in Example 1 and then evaluated for the attacking property and the heat resistance. The results are shown together with the results for Example 1 in Table 3.
  • the content proportion of the benzothiazole compound (S1) is preferably no less than 0.25% by mass and no more than 2% by mass and especially preferably no less than 0.5% by mass and no more than 2% by mass of the total amount of the lubricant composition.
  • Example 14 Besides setting the amount of the dithiocarbamate compound (S2) as the antioxidant to 0.5 g (Example 14), 1 g (Example 15), and 3 g (Example 16), lubricant compositions were produced in the same manner as in Example 2 and then evaluated for the attacking property and the heat resistance. The results are shown together with the results for Example 2 in Table 4.
  • the content proportion of the dithiocarbamate compound (S2) is preferably no less than 0.5% by mass and no more than 3% bymass and especially preferably no less than 1% by mass and no more than 3% by mass of the total amount of the lubricant composition.
  • Example 17 Besides setting the amount of the mercaptobenzimidazole compound (S3) as the antioxidant to 0.5 g (Example 17), 2 g (Example 18), and 3 g (Example 19), lubricant compositions were produced in the same manner as in Example 3 and then evaluated for the attacking property and the heat resistance. The results are shown together with the results for Example 3 in Table 5.
  • the content proportion of the mercaptobenzimidazole compound (S3) is preferably no less than 0.5% by mass and no more than 3% by mass and especially preferably no less than 1% by mass and no more than 3% by mass of the total amount of the lubricant composition.
  • Example 20 Besides setting the amount of the benzothiazole compound (S4) as the antioxidant to 1 g (Example 20), 3 g (Example 21), and 4 g (Example 22), lubricant compositions were produced in the same manner as in Example 4 and then evaluated for the attacking property and the heat resistance. The results are shown together with the results for Example 4 in Table 6.
  • the content proportion of the benzothiazole compound (S4) is preferably no less than 1% by mass and no more than 4% by mass and especially preferably no less than 2% by mass and no more than 4% by mass of the total amount of the lubricant composition.
  • Electric power steering apparatus 9 : Steering mechanism, 17 : Electric motor, 18 : Speed reduction gear, 19 : Small gear, 20 : Large gear

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Chemistry (AREA)
  • Lubricants (AREA)
  • General Details Of Gearings (AREA)
  • Power Steering Mechanism (AREA)
US13/119,029 2008-10-16 2009-10-14 Lubricant composition, speed reduction gear, and electric power steering apparatus Active 2030-05-08 US8513171B2 (en)

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JP5694740B2 (ja) * 2010-11-08 2015-04-01 株式会社ジェイテクト 潤滑剤組成物、減速機および電動パワーステアリング装置
JP2013209625A (ja) * 2012-02-27 2013-10-10 Kobe Steel Ltd 塑性加工用水溶性潤滑剤、塑性加工用金属材および金属加工品
DE102012105543A1 (de) * 2012-06-26 2014-03-20 Zf Lenksysteme Gmbh Planetengetriebe mit fettschmierung
JP2014080991A (ja) * 2012-10-12 2014-05-08 Jtekt Corp 減速機、および電動パワーステアリング装置
JP5988097B2 (ja) * 2012-10-12 2016-09-07 株式会社ジェイテクト 減速機、および電動パワーステアリング装置
JP6292569B2 (ja) * 2013-12-04 2018-03-14 協同油脂株式会社 等速ジョイント用グリース組成物及びそのグリース組成物を封入した等速ジョイント
JP2016121296A (ja) * 2014-12-25 2016-07-07 株式会社ジェイテクト グリース組成物およびスプライン伸縮軸
CN109097173A (zh) * 2018-08-01 2018-12-28 苏州力森克液压设备有限公司 一种用于液压缸的皂基型润滑脂
EP3845622B1 (en) 2020-01-03 2024-08-21 Indian Oil Corporation Limited High temperature zinc complex grease
JP7530731B2 (ja) * 2020-03-31 2024-08-08 協同油脂株式会社 ラックアシストタイプ電動パワーステアリングのボールねじ部用グリース組成物
WO2023190513A1 (ja) * 2022-03-28 2023-10-05 協同油脂株式会社 グリース組成物及び前記グリース組成物を充填したラックアンドピニオン式ステアリング装置

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WO2010044259A1 (ja) 2010-04-22
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JP5403989B2 (ja) 2014-01-29
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EP2338957A4 (en) 2012-04-25
EP2338957B1 (en) 2018-08-08

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